.yy::before {
    content: "";
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
    background-color: rgba(0, 0, 0, .3);
}

.yy {
    background-image: url('/img/bg/2021.jpg');
    background-repeat: no-repeat;
    background-size: cover;
    background-position: center center;
    background-origin: border-box;
    width: 100%;
    height: 100vh;
    background-attachment: fixed;
    z-index: -1;
}

.app-footer {
    /*position: absolute;*/
    right: 0;
    bottom: 0;
    left: 0;
    z-index: 100;
}

.a-none {
    color: inherit;
    text-decoration: none;
    cursor: pointer;
}

/* (全局)补充样式 */
p > code {
    background: #eeeeeeaa;
}

pre {
    background: #eeeeeeaa;
}